1. Field of the Invention
The present invention relates to a scroll compressor which is installed in an air conditioner, a refrigerator, or the like.
2. Description of the Related Art
In conventional scroll compressors, a fixed scroll and a swiveling scroll are provided by engaging their spiral wall bodies, and fluid inside a compression chamber, formed between the wall bodies, is compressed by gradually reducing the capacity of the compression chamber as the swiveling scroll revolves around the fixed scroll.
The compression ratio in design of the scroll compressor is the ratio of the maximum capacity of the compression chamber (the capacity at the point when the compression chamber is formed by the meshing of the wall bodies) to the minimum capacity of the compression chamber (the capacity immediately before the wall bodies become unmeshed and the compression chamber disappears), and is expressed by the following equation (I).Vi={A(θsuc)·L}/{A(θtop)·L}=A(θsuc)/A(θtop)  (I)
In equation (I), A(θ) is a function expressing the cross-sectional area parallel to the rotation face of the compression chamber which alters the capacity in accordance with the rotating angle θ of the swiveling scroll; θsuc is the rotating angle of the swiveling scroll when the compression chamber reaches its maximum capacity, θtop is the rotating angle of the swiveling scroll when the compression chamber reaches its minimum capacity, and L is the wrap (overlap) length of the wall bodies.
Conventionally, in order to increase the compression ratio Vi of the scroll compressor, the number of windings of the wall bodies of the both scrolls is increased to increase the cross-sectional area A(θ) of the compression chamber at maximum capacity. However, in the conventional method of increasing the number of windings of the wall bodies, the external shape of the scrolls is enlarged, increasing the size of the compressor; for this reason, it is difficult to use this method in an air conditioner for vehicles and the like which have strict size restrictions.
In an attempt to solve the above problems, Japanese Examined Patent Application, Second Publication, No. Sho 60-17956 (Japanese Unexamined Patent Application, First Publication, No. Sho 58-30494) proposes a scroll compressor in which the spiral top edge of each wall of a fixed scroll and a swiveling scrollwall body have a low center side and a high outer peripheral side to form a step, and the side faces of the end plates of both scrolls have high center sides and low outer peripheral sides in correspondence with the step of the top edge.
In the scroll compressor as described above, when the wrap length of the compression chamber at maximum capacity is expressed as L1 and the wrap length of the compression chamber at minimum capacity is expressed as Ls, the compression ratio Vi′ for design purposes is expressed by the following equation (II).
 Vi′={A(θsuc)·L1}/{A(θtop)·Ls}  (II)
In equation (II), the wrap length L1 of the compression chamber at maximum capacity is greater than the wrap length Ls of the compression chamber at minimum capacity, so that L1/Ls>1. Therefore, the compression ratio in design can be increased without increasing the number of windings of the wall bodies.
The scroll compressor which uses scrolls having steps as described above has a problem of airtightness when a join edge, which joins the low top edge and high top edge of the wall bodies, slides against a join wall face, which joins the deep side face and the shallow side face of the end plate.
For this reason, the scrolls are processed and assembled with extremely high precision in order to preserve airtightness when sliding the join wall faces together. However, the demand for extremely high-precision processing and assembly leads to poor productivity and higher costs.
To solve the above problems, Japanese Unexamined Patent Application, First Publication, No. Hei 6-10857 discloses a constitution in which a sealing member is provided on a join edge of the wall body of one scroll, and an energizing member is used to press the sealing member against the contact wall face of the end plate of the other scroll (see FIGS. 5 and 6).
In the above method, a sealing member is provided on the join edge of the wall body of one scroll and slides against the contact wall face of the side plate of the other scroll, enabling airtightness to be preserved without requiring high-precision processing. However, there is a problem that the sealing member may fall off when a gap appears between the join edge of the wall body and the join wall face of the end plate.
In order to solve the problem, Japanese Unexamined Patent Application, First Publication, No. Hei 8-28461 discloses a scroll compressor in which the sealing member, which is provided on the join edge of the wall body, is formed in one piece with the tip seal, which seals the upper top edge of the spiral-shaped wall body, thereby preserving airtightness and preventing the sealing member from falling off when the join wall faces are separated (see FIGS. 12 and 13).
However, the above method has the following problems. Although the tip seal and the sealing member of the join wall face are provided in one piece, since the sealing member is joined to the tip seal like a cantilever, the sealing member tends to break during long time operation.
Furthermore, in the conventional scroll compressor, the tip seal is provided along the spiral-shaped top edge of the wall body, preserving airtightness between the bottom faces of the scrolls and obtaining a compression chamber with negligible leakage, increasing the compression efficiency.
In the scroll compressor using a step in the scroll as described above, the tip seal is separated by the top edge of the stepped wall body, however, in the tip seal positioned on the outer peripheral side of the scroll, sufficient pressing force cannot be achieved against the top edge of the wall bodies due to low pressure against the rear faces thereof, and the tip seal cannot function properly as a seal. When there is considerable leakage from the compression chamber, an equivalent dynamic force is needed for recompression and dynamic force loss of the driving power is incurred; this is not efficient.